The present invention relates to a flame-retardant building material having excellent performance characteristics as heat and sound insulation and suitable for shaping into various kinds of board materials, e.g. for ceilings and walls, as well as for the use as a blow-in or blow-on insulating material. It also relates to a method for making same.
Needless to say, there are currently in use in the building industry a great variety of building materials depending on the requirements for the particular building and locality. The requirements for the building materials are so diversified that one material suitable in a building is not always useful in another. Several characteristics are, however, almost always important in any type of building materials among which, for example, are mechanical strength, nonflammability or flame retardancy and heat and sound insulation as well as inexpensiveness.
In relation to the inexpensiveness of the building materials, there may be obtained two-way advantages simultaneously if an industrial waste can be processed or fabricated into building materials having satisfactory characteristics. These are the solution of the problem caused by the burdensome waste material such as environmental pollution and the commercial benefit obtained with the building materials produced therefrom with outstanding inexpensiveness.
Accordingly there have been made various attempts to utilize useless industrial waste materials for the production of building materials. Unfortunately there are very few examples of success in which excellent building materials suitable for practical use are manufactured from an otherwise useless or rather harmful industrial waste as the main starting material.
Aluminum fabrication plants provide particularly notorious problems due to the difficulties in waste disposal. As is well known, aluminum articles in recent years are used rarely in the as-shaped condition but almost always used after surface finishing.
The method of surface finishing most widely undertaken in the aluminum industry is, of course, a surface anodization in which the surface of the aluminum article is electrolytically oxidized in an acidic electrolyte bath resulting in a thin but dense layer of aluminum oxide and evidencing increased chemical and physical stability as well as beauty. A problem in the anodization treatment of aluminum articles is that a considerable amount of aluminum metal unavoidably is dissolved in the electrolyte bath and the thus dissolved aluminum finally precipitates in the form of amorphous aluminum hydroxide forming a gel-like sludge when the electrolyte solution is neutralized for sewage disposal.
The gel-like sludge usually contains large volumes, e.g. 70 to 90% by weight, of water but is filtrable with great difficulty so that drying up of such an aluminum hydroxide sludge is practically impossible. Therefore, the only way in the art for the disposal of the aluminum hydroxide sludge is to discard it in a land fill or in the ocean in its gel-like form.
Such a method of waste disposal is, of course, not quite acceptable even setting aside the problem of the large cost for the transportation of such a watery waste material to the land fill or to the ocean. For example, a reclaimed land filled with such a gel-like sludge is naturally weak in yield strength of the ground resulting in a decreased utilizability of the land. Discarding of the sludge in the ocean is also faced with regulations to prevent pollution of water. Thus the waste disposal of the gel-like aluminum hydroxide sludge has been the most troublesome problem in the aluminum fabrication industry.
In a copending application Ser. No. 327,021, filed Dec. 3, 1981, the inventors have previously proposed a novel building material with excellent performance of heat and sound insulation as well as flame retardancy manufactured on the basis of the above described very noxious aluminum hydroxide sludge. Application No. 55-178211). The building materials proposed there, however, have several problems in the manufacturing process thereof.
For example, the manufacturing process must be performed by use of a strong alkali such as sodium hydroxide and a strong acid such as phosphoric acid so that accidents are sometimes unavoidable even when good protective means are provided. Further, the manufacturing process should be performed in several steps so that the process is time-consuming and relatively difficult to control. In addition, the process involves a step of slurrying the materials by the addition of a considerable volume of water and the subsequent removal of the water by filtration necessarily takes much labor and time not to mention the problem of sewage disposal of the large volume of polluted water.